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Tracking Elusive Iguanas One Swab at a Time

By Jeroen van Kuijk and Dr. Kat Stewart, Institute of Environmental Sciences, Leiden University

It can be a tough challenge to spot iguanas in the field. Sometimes it feels like searching for a needle in a haystack. Locating and monitoring iguana populations has typically been a painstaking and time-consuming task. Researchers often have to rely on visual sightings or set up traps, both of which have limitations. Not to mention, many iguana species are expert hiders, making them exceedingly difficult to find in their environment. But what if there was a way to detect their presence without ever laying eyes on them? Enter environmental DNA (eDNA)!

It can be a challenge to find iguanas like these Lesser Antillean Iguanas (Iguana delicatissima) in their habitat since they blend in so well with their surroundings.

The Power of Environmental DNA

The use of eDNA is a revolutionary tool that can transform the way we track and study these iconic reptiles. Unlike traditional methods, eDNA allows us to detect the presence of iguanas by simply collecting water or samples from surfaces in their habitat. A simple swab or scoop is all that’s required to check if any iguanas are tucked away nearby. It’s a game-changer!

The concept behind eDNA is really straightforward. Every organism, whether it’s a majestic blue whale swimming through the ocean or a small lizard hiding in the trees, leaves traces of itself behind. This includes shed skin, feces, urine, and other bodily secretions. Even if we can’t see the iguanas, they still leave their genetic footprint in the environment. By sampling these traces, we can identify the presence of iguanas in any given location, even when the animals themselves remain hidden from view. This non-invasive method not only saves time and resources but also reduces stress on the animals and their habitats.

At Rotterdam Zoo, the team tested the eDNA toolkit by collecting samples from surfaces in the Lesser Antillean Iguana exhibit. 

Trials and Evaluations

A grant from the International Iguana Foundation enabled us to start a pioneering pilot study this year. It was aimed at identifying the presence of iguanas and classifying them as native, invasive, or possibly hybrids, using a newly designed eDNA toolkit. Our toolkit underwent rigorous testing, involving trials on blood samples, and an ex-situ evaluation at an iguana exhibit at the Rotterdam Zoo.

During the testing phase, we aimed to extract DNA fragments from our samples, to see if it would be possible to collect enough DNA for genotyping. After days of extracting samples and pipetting—and convincing a pipetting robot to function—we were able to successfully determine the genotypes of our blood samples.

Following this successful testing, we proceeded to gather environmental swabs from the Lesser Antillean Iguana (Iguana delicatissima) exhibit at the Rotterdam Zoo. We were able to extract an ample supply of DNA fragments from the environmental swabs. They were genotyped and accurately determined the corresponding species. Yes! Just what we were hoping for.

The next step for this project will be to do some testing in the field, taking samples in wild habitat and analyzing them to determine what species information we can gather. Ultimately, the goal is to make eDNA test kits available to iguana field researchers so they can find out what species are present in their field sites, information that can be used for conservation planning.

Applications and Benefits

The applications of environmental DNA in iguana research—and other wildlife research—are vast. Conservationists can use eDNA to monitor the distribution of invasive iguana species, helping to manage and mitigate their impact on native ecosystems. Researchers can also gain insights into iguana behavior, population dynamics, and habitat preferences, all without disturbing the animals or their surroundings.

Furthermore, eDNA can aid in the discovery of previously unknown iguana populations—such as invasive non-native iguanas—shedding light on their hidden existence among the native population. This technology is not limited to iguanas alone and has been successfully employed in the study of various other elusive and endangered species worldwide. It has a world of possibilities!

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